Year: 2016
Type: conference-abstract
Abstract: Dendritic cell (DC) vaccines currently in phase III trials for glioblastoma use autologous tumor lysate (ATL) as an antigen source to induce a lymphocytic infiltration but it remains unclear what epitopes this immune response is specifically directed against. We hypothesized that the most immunologically relevant target antigens in the ATL are neoantigen peptides arising from tumor-specific mutations. To test this, we identified non-synonymous coding mutations in the GL261 murine glioma cell line and human GBM samples using whole exome seq, RNAseq, and bioinformatics software to predict the mutated sequences which result in enhanced peptide-MHC binding. Nine candidate neoantigens were identified from the GL261 glioma line. Mice bearing intracranial GL261 gliomas were vaccinated with control, ATL, or neoantigen-pulsed DC vaccination. Tumor-infiltrating lymphocytes (TILs) were isolated and co-cultured with DCs pulsed with peptides containing the neoantigen sequences for flow cytometry. 5x105 -2x106 TILs were recovered from vaccine-treated animals, whereas <105 were recovered from controls, indicating a enhanced T cell infiltration due to the vaccine.Ex vivo restimulation induced CD69 upregulation in 0, 21, and 26% of TILs in control, ATL, and neoantigen-pulsed DC vax treatment groups, respectively. Survival was significantly extended similarly in both ATL and neoantigen-pulsed DC vax treatment groups compared with control treatment (P<0.02). In human GBM patients, we identified an average of 15 strong binding and 9 weak binding neoantigens per tumor from 8 patients treated with ATL DC vaccination. TCR sequencing from the original tumor and TIL cultures revealed common high-frequency TCR clonotypes. Together, these studies indicate that tumor lysate DC vaccines are capable of priming CD8+ T cell responses directed at tumor-specific mutations in mice. Further studies are underway to characterize the immune responses to these candidate neoantigens in human patients following ATL-pulsed DC Therapy.
Source: Neuro-Oncology
Language: English
Subfield: Immunology
Field: Immunology and Microbiology
Domain: Life Sciences
Open Access status: bronze
OpenAlex ID: W2587594383